EP0056726A1

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Info

Publication number: EP0056726A1
Application number: EP82300263A
Authority: EP
Inventors: Robert Gilbert Bosshard; Alexander Ian Mc Intosh
Original assignee: Australian Meat and Live Stock Research and Development Corp
Current assignee: Australian Meat and Live Stock Research and Development Corp
Priority date: 1981-01-21
Filing date: 1982-01-19
Publication date: 1982-07-28
Also published as: NZ199520A; EP0056726B1; CA1195759A; DE3276546D1; AR230133A1; ZA82348B

Abstract

An electronic system for the remote identification of objects such as livestock comprising a transponder (A-G) having a predetermined code stored therein positioned on the object to be identified, and an interrogator for remotely interrogating said transponder; the transponder has comparator means (18) for comparing the decoded VHF signal from the interrogator with a stored code wherein a valid comparison initiates the transmission of a return signal (f3) which actuates an automatic direction finder (ADF) in the interrogator.

Description

This invention relates to an electronic system for the remote identification of objects. In particular, the invention is directed to the remote identification of livestock, although it is not limited thereto.
The advantages of remote electronic identification of livestock are well known. Remote identification avoids injury and trauma to both the operator and the animal. Also, electronic identification provides rapid and reliable identification and allows large numbers of livestock to be monitored. Due to the ever-increasing sizes of herds, manual methods are not only tedious but also no longer practicable.
A system for the remote electronic identification of livestock is disclosed in U.S. Patent No. 4,075,632 to Baldwin et al. The Baldwin patent teaches an electronic identification system comprising an implantable transponder which receives an unmodulated radio frequency signal from a transmitter/receiver. The transponder amplitude modulates the signal with predetermined uniquely coded information and reflects or re-transmits it to the transmitter/receiver. Decoding of the reflected signal allows the transponder to be identified.
It has been found in practice that the system of Patent No. 4,075,632 is not entirely suitable for locating specific animals. Transmission of the radio frequency carrier signal to a herd of animals, each having a coded transponder, will generate a plurality of instantaneous responses, each being the transmitted signal as modulated and reflected by each respective transponder. Weaker reflections may be "swamped" by stronger return signals from closer animals, and consequently not recorded. Also, while the presence of a particular animal may be recognised, its location within the herd will be unknown.
The known system uses a frequency in the upper UHF region. The maximum operating range with that frequency has been found to be of the order of only 2-3 metres.
Moreover, at this frequency, animals standing behind obstacles such as other livestock, trees, etc., may be shielded from the interrogating signal and their presence may not be detected by the interrogator.
Research within the scope of the present invention has shown that the choice of carrier frequency is critical to the operation of the electronic identification system. High frequencies, such as those above 200 MHz, allow the use of small aerials in the transponder. However, with implanted transponders, high frequency signals are greatly attenuated by the animal's skin. Consequently, the range of operation is limited to close quarters, i.e. less than about one metre.
It should also be noted that operation at the higher microwave frequencies has the inherent disadvantage that both operator and livestock are exposed to fairly high levels of microwave radiation. Known microwave systems for identifying railway rolling stock, for example, are not suitable for livestock identification.
The lower radio frequencies are not attenuated as much during transmission through the animal's skin. However, at frequencies below VHF, the efficiency of the aerial is reduced. More power is required to maintain the same operating range thereby causing a greater current drain on the transponder's battery. As the transponder is implanted in the animal, the battery life should last at least as long as the life of the animal.
The availability and falling costs of microprocessors makes on-farm computers feasible. Computer control allows flexibility of operation as well as large scale reliable operation. However, many of the known electronic systems of identification are hard-wired and unsuitable for software control.
It is an objection of the present invention to overcome or substantially ameliorate the above described disadvantages.
According to the present invention, there is disclosed a system for the remote electronic identification of objects, said system comprising at least one transponder to be positioned on a respective object to be identified and/or located, said transponder being capable of having a predetermined code stored therein, and an interrogator for remotely interrogating said transponder(s);
said transponder comprising first receiving means for receiving a coded VHF signal, decoding means connected to said receiving means for decoding said first signal, comparator means for comparing said decoded signal with said stored code, and frequency generating means connected to said comparator means, said frequency generating means being able to transmit a return signal at a second frequency in response to a valid comparison by said comparator means.
The interrogator preferably comprises a transmitter for transmitting the coded VHF signal, receiving means for receiving the return signal, and an automatic direction finder connected to the receiving means and responsive to the return signal for indicating the direction of the transponder with respect to the interrogator. Thus, a particular animal whose code is known can be located.
Using a carrier frequency of 150 MHz, an operating range of approximately 40 metres has been achieved using a device according to the preferred embodiment described hereinafter.
Preferably, the interrogator also comprises programmable control means, such as a microprocessor, which can vary the code of the coded VHF signal either in response to manual instructions or in accordance with a stored program. For example, in identifying the members of a particular herd of animals, the control means may be programmed to run through all possible codes of those animals. As each animal's code is transmitted, it will transmit the return signal and its presence will be recorded. To determine if a particular animal is within the herd, its code can be manually input to the control means which causes the transmitter to transmit that particular code. If a return signal is received, the presence of that particular animal is established.
Advantageously, the transponder is miniaturised and implanted under the skin of the animal at an early stage.
The invention will now be described in more detail with reference to a preferred embodiment thereof as illustrated in the accompanying drawings in which:

Fig. 1 is a schematic diagram of the transponder of the preferred embodiment;
Fig. 2 is a schematic diagram of the interrogator of the preferred embodiment;
Fig. 3 depicts wave forms of sample signals suitable for use with the preferred embodiment;
Fig. 4 shows circuit details of the 16 bits encoded;
Fig. 5 shows circuit details of the 16 bits decoded on the transponder; and
Fig. 6 shows circuit details of the oscillator in the transponder.

Turning to Fig. 1, the transponder of the preferred embodiment can receive signals from the interrogator, store a previously coded identification number and return a signal to the interrogator when the received coded signal is identical to that stored.
The transpoder comprises an antenna A which is used for both receiving and transmitting signals. A first receiving section B is connected to the antenna A and tuned to a first frequency f_l. This tuning can be provided by aband pass filter 10. When a signal of frequency fl is received, it passes through theband pass filter 10 to arectifier 12 and alow pass filter 14 to close a timer switch C. Typically, the timer switch C is enabled for a period of 5 seconds on each triggering. Once activated by the receiver section B the switch C allows a second receiver section D to be powered from a local battery E.
The second receiver section D operates at a second VHF frequency f_2' preferably 150 MHz, and comprises adecoder 18 which decodes the received coded VHF signal and compares the code derived therefrom with a code previously stored in the transponder. Upon a positive comparison, a second timer switch F, connected between the local battery E and anoscillator 22 is closed for approximately 34 seconds. Theoscillator 22 generates a return signal of frequency f₃ which is re-transmitted via antenna A. Typically, the oscillator is a quartz crystal to achieve stable oscillation with low power drain from the battery.
The use of two receiver sections B and D, and the corresponding timer switches C and F, ensures that the transponder battery E powers the second receiver section D andoscillator 22, in the correct sequence, when, and only when, interrogation is taking place.
The transponder of the preferred embodiment is approximately 3 cm in length, 1.5 cm in width, and 1 cm in depth. The transponder is able to be implanted under the skin of an animal at an early age, and the low current drain ensures that the battery will last for the life of the animal thereby obviating the need for removal of the transponder for battery replacement.
The interrogator shown in Fig. 2 comprises two radio transmitters sharing a common aerial and a radio receiver having an automatic direction finder associated therewith, together with associated controls and display. The electronic apparatus of the interrogator can be encased in a housing (not shown) which can be carried and operated by an unskilled individual on foot, horseback, or in a vehicle.
The interrogator is controlled by a control unit I which typically comprises a microprocessor such as the Rockwell AIM 65 model. However, a microprocessor can be custom designed for the application of the present invention. The control unit I has a keyboard J by which commands may be input. In performing an identication or location task, the control unit I will cause the transmitter B to transmit a signal of frequency f_l via the antenna A to thereby activate the transponder. The control unit I also provides the desired code for an encoder C. This code is used to modulate a VHF signal from oscillator 40 in the modulator D. The coded signal is then amplified by RF amplifier E before being transitted to the transponder via antenna A.
In the preferred embodiment, the code is a digital code comprising a 24 bit word. It will be obvious to those skilled in the art that the number of bits can be varied to suit the particular application. The digital code word is provided to the encoder C by the control unit I in parallel form. The encoder C performs a parallel to serial conversion of the 24 bits which are then clocked through to the modulator.
The particular coding used in the preferred embodiment is illustrated in Fig. 3. The binary value "1" is represented by a pulse in the first half of the bit period, while the binary value "0" is represented by a pulse in the second half of the bit period. This coding technique ensures that there is a pulse in each bit period, and enables a clock to be derived by the transponder from the coded signal using one-shot multi-vibrators. Thus, there is no need for an internal clock in the transponder.
In the preferred embodiment, the VHF signal is amplitude modulated by the digital code word, but other known modulation techniques can be used. The demodulating and decoding techniques applied in thedecoder 18 of the transponder are the reverse of the modulating and encoding techniques used in the interrogator.
The interrogator also comprises an antenna F, receiver G having an automatic direction finder, and a display H connected thereto. Thus, the direction of the transponder with respect to the interrogator can be determined from the return signal which is transmitted byoscillator 22 of the transponder when a positive comparison between the transmitted code signal and the stored code is made. The display H may be either a rotating mechanical pointer or an array of light emitting diodes arranged in a suitable way to indicate the direction with the required angular resolution. The use of an LED array has the advantage of greater robustness.
The 24 bit digital code word can be divided into a number of bit groups which represent region, animal type, animal characteristics such as sex, date of birth, weight, breeding record, fate, etc. This information can be stored in the control unit I.
An alpha-numeric display K is connected to the control unit so that results of identification runs can be displayed. The control unit can also be connected to one or more external devices such as printers, recording units using magnetic tapes or discs, and computers for recording or providing information.
As the control unit is programmable, its mode of operation can be varied to suit particular applications. The preferred embodiment can be operated in three different modes or combinations of these according to which task it is required to perform. The three modes are described by way of illustrative examples below.

A. Automatic recording of identification numbers of all animals in an enclosed space or yard.

The interrogator is placed at a suitable location so the animals whose numbers are to be recorded are within the operating range of the system. Upon input of the appropriate command to the control unit I, the interrogator will automatically carry out the following sequence of operations:

(i) A VHF signal of frequency fl is sent to activate the on-animal transponders.
(ii) The codes corresponding to the decimal numbers 0000 to 9999 are generated and transmitted in sequence. The time to generate and transmit the entire sequence is approximately 2 seconds. If there are more than 10,000 animals within the range of operation, the range of codes can be increased.
(iii) Whenever a transmitted code matches that stored in the transponder of an animal present, the transponder sends a reply signal which is received by the interrogator and recognised by the control unit. The control unit then stops the scanning of the codes temporarily.
(iv) The interrogator then transmits this code as a check. If the transponder again replies, that particular code is stored by the interrogator thereby indicating that the animal of that code is in the herd. A method of locating the animal is described below.
(v) The scan of the codes continues and the process of recognition and storing of codes corresponding to the animals present continues until the entire sequence is exhausted. Upon receipt of further instructions through the keyboard, the interrogator will then display the stored codes or transfer them to a printer or other external device.

_B. Identification of a particular animal.

When a particular animal whose number is unknown needs to be identified, the interrogator is enabled and as in the previous mode, scans through the available codes until a reply is received by the transponder indicating that the transmitted code and that stored in the transponder are identical. A check signal is sought by re-transmitting the code as in example A. The identification number is then displayed and according to instructions entered through the keyboard, previously stored information about that animal may be recalled and displayed. This information can also be updated if required.

In the event of any ambiguity about which particular on-animal transponder has replied, the interrogator may be switched to the locating mode described below.

C. Automatic recording of identification numbers of all animals passing through a race.

The range of the system is reduced to approximately one metre by an appropriate reduction in the strength of the signal used to activate the transponders. The interrogator is fixed in position and the animals caused to pass through a race or similar obstruction so that they come within the (reduced) range of the transponder not more frequently than one animal every two seconds, this being the time required for a complete scan and transmission of all the codes between (decimal) 0000 and 9999. The system then operates as in example B, except that the identification numbers are stored for later display or transmission to other devices as in example A.

D. Location of a particular animal.

The identification code of a required animal is entered through the keyboard. The interrogator sends a sequence of enabling signals simultaneously with the coded signal. Once the transponder is in the range of the interrogator, it will send its reply signal, and with the interrogator switched to the "locate" mode, the display of the automatic direction finder will continually indicate the direction from the interrogator to the activated transponder. If the transponder changes location, the automatic direction finder display will track the animal by pointing in the new direction.

The foregoing description is given by way of example rather than limitation. The system is able to identify and/or locate any one or all of a large number of animals or other objects. It thus lends itself to many other applications in which the value and/or lifetime of the objects are sufficient to justify the cost of the transponders. For example, the invention can be used for stock control in large warehouses and storeyards, location of railway stock in a railway shunting yard, identification and recording of the rolling stock used in a particular train as it passes a fixed point, and similar management of shipping containers. In other areas the transponders could be used repeatedly by making them detachable from the identified objects and using computer control to associate the re-cycling tags with the objects. Areas for application of the system in this way include the sorting, identification and location of mailbags in the Post Office, the automatic recording of animal carcases in an abattoir and the management of individual items on a production line of the type used in automotive manufacturing.